The present invention relates to a nitride film forming method, a semiconductor device fabrication method, a capacitor fabrication method and a nitride film forming apparatus, more specifically, a nitride film forming method which can form nitride film of good quality, a semiconductor device fabrication method using the nitride film forming method, a capacitor fabrication method and a nitride film forming apparatus to be used in the nitride film forming method.
Conventionally, silicon oxide film has been widely used as a material of the gate insulation film of transistors.
However, silicon oxide film has an about 4.0 dielectric constant which is relatively low and a 10 MV/cm voltage resistance which is not sufficiently high. For further micronization and speed-up of transistors, it is necessary to use a material of high dielectric constant and high voltage resistance as a material of the gate insulation film. When silicon oxide film is used as a material of the gate insulation film, boron implanted in the gate electrodes of transistors often passes through the gate insulation film and arrives at the semiconductor substrate.
Recently, it is noted to use as a material of the gate insulation film silicon nitride film having an about 7.2 dielectric constant, which is relatively high, and a relatively high voltage resistance. The use of silicon nitride film as a material of the gate insulation film can prevent boron in the gate electrodes from arriving at the semiconductor substrate.
When a silicon nitride film is formed on a silicon substrate by thermal nitriding, the thermal processing temperature must be set very high. When the thermal processing temperature is set very high, there is a risk that the semiconductor substrate, etc. may be damaged. Then, the method of forming a silicon oxide film on a silicon substrate and heating the silicon substrate in a nitriding atmosphere to thereby form a silicon nitride film on a part of the silicon oxide film or in the interface between the silicon oxide film and the silicon substrate is proposed. The thus formed film is called a nitride oxide film.
When ammonia gas is used as the nitriding atmosphere, the nitriding takes pace in the silicon oxide film, and the interface between the silicon oxide film and the silicon substrate. When nitrogen monoxide is used as the nitriding atmosphere, the nitriding takes place between the silicon oxide film and the silicon substrate.
A nitriding technique using plasma radicals is also proposed.
Following references disclose the background art of the present invention.    [Non-Patent Reference 1]    Surface Science, Vol. 25, No. 10, p. 618-627 (2004)
However, the nitride film formed by using ammonia gas does not have good microroughness in the surface. When nitrogen monoxide is used, the silicon nitride film is formed only in the interface between the silicon oxide film and the silicon substrate. When the nitride film is formed by using plasma radicals, there is a risk that the semiconductor substrate, etc. may be damaged.